This invention relates to voltage regulators and more particularly to such a regulator having a temperature dependent output.
The power supply of an avalanche photodetector (APD) used in fiber optic communications systems or similar optical detection systems is required to have a value of 325 to 450 volts DC as determined by each individual unit and to have a temperature dependence of +2 volts per degree centigrade to maintain a constant avalanche gain. Conventional techniques employed to achieve such regulation have used temperature sensitive elements such as thermistors which have a percentage change of resistance per degree change of temperature as determined by the thermistor composition. In order to adapt such temperature sensitive elements to the power requirement of an avalanche photodetector, sophisticated linearization networks are used with the elements. An example of such a network is described in Temperature Measurement Handbook published by Omega Engineering, Inc., Stamford, Connecticut. Such networks are not only costly and time consuming to design, but they also are inflexible in that the resultant resistance-temperature characteristic cannot be varied without redesigning the network. This invention is directed to an improved voltage regulator which provides the desired regulation for APDs without such linearization networks.